Device for starting or recommencing spinning of a yarn in a friction spinning apparatus

ABSTRACT

In order to start or recommence spinning of a yarn in a friction spinning apparatus, in the course of starting of spinning or piecing after a yarn break, by means of a fiber transport duct, fibers separated by an opening device, are delivered to a rotating friction spinning drum and twisted to form a twisted fiber structure. When the twisted fiber structure has reached a substantially predetermined diameter, the twisted fiber structure is moved by an airstream delivered from a pressure air infeed channel towards and into a guide tube and from that location, into the convergent space of rotating withdrawal rolls. The twisted fiber structure is entrained at production speed by these withdrawal rolls and is delivered to the diverging or outlet side of the withdrawal rolls to a suction device placed in readiness. This suction device can transfer the formed yarn following the twisted fiber structure to the succeeding or downstream elements provided for further processing.

CROSS-REFERENCE TO RELATED PATENTS

This application is related to the commonly assigned, U.S. Pat. No4,646,513, granted Mar. 3, 1987, entitled "METHOD FOR PIECING A YARN INA FRICTION SPINNING DEVICE" and the commonly assigned, U.S. Pat. No.4,680,924, granted July 21, 1987, entitled "METHOD OF STARTING SPINNINGOF A YARN IN A FRICTION SPINNING DEVICE".

This application is also related to our commonly assigned, co-pendingU.S. application Ser. No. 07/203,061, filed June 6, 1988, and entitled"METHOD OF, AND DEVICE FOR, PERFORMING A START SPINNING OPERATION FORSPINNING OF A YARN IN A FRICTION SPINNING APPARATUS", to which referencemay be readily had.

BACKGROUND OF THE INVENTION

The present invention broadly relates to a new and improved constructionof a device for performing a start spinning operation, namely, startingor recommencing spinning of a yarn or the like in a friction spinningapparatus.

In its more particular aspects, the device for starting or recommencingspinning of a yarn in a friction spinning apparatus comprises frictionspinning means containing a friction spinning surface provided thereonto which fibers are delivered. The fibers are formed into a twistedfiber structure or lap at a yarn formation position of the frictionspinning means during the starting or recommencing of the spinningoperation. The twisted fiber structure is withdrawn by a yarn withdrawalmeans, typically, a yarn withdrawal roller pair.

Previously known devices for the above-mentioned start spinning of ayarn, employ a yarn end withdrawn from a package. This yarn end isinserted into the stationary friction spinning means for start spinningand thereafter the start spinning operation is carried out at reducedspeed of the friction spinning apparatus by feeding fibers to the yarnend withdrawn from the package. It has also been proposed that prior tostart spinning, that is, before feed of freely floating fibers to thereturned yarn end, the latter should be untwisted by movement of thefriction spinning means in an opposite direction to enable betterconnection or interlacing of the delivered fibers with the yarn end.

Such a device is known from German Published Patent Application No.3,318,687, in which a yarn end from a reverse rotated package istaken-up by a suction device and the yarn drawn-in by suction is held bymeans of two reciprocating devices in the convergent zone of twostationary friction spinning drums.

Before delivery of freely floating fibers to this yarn, the yarn isopened by reverse rotation of the friction spinning drums so that thefibers lie in a substantially twist-free condition in the convergentzone of the friction spinning drums. Thereafter, the friction spinningdrums are placed into operation with reduced rotational speed in thenormal direction of rotation and freely floating fibers are delivered tothe opened yarn. The yarn which is thus produced, is withdrawn at acorrespondingly reduced speed and delivered to a joining or connectionmeans.

In order to take-up the continuously delivered yarn operation, thedelivered yarn is received by a suction nozzle functioning as a yarnstore or storage.

After completion of the joining or connection operation, the completedevice is accelerated to the operating speed and thereafter isdisconnected from the necessary auxiliary drive means and is driven bythe normal drive means at the operating speed.

Certain of the disadvantages of a device of this type reside in thelarge amount of auxiliary equipment needed for the start spinningoperation.

In the aforementioned U.S. Pat. No. 4,680,924, there is disclosed amethod of start spinning of a yarn in a friction spinning device. Freelyfloating fibers are forwarded to a yarn formation position where suchfreely floating fibers are formed into a twisted fiber structure of acertain size. An airstream is used to forward the twisted fiberstructure towards yarn withdrawal rolls. A shortcoming of sucharrangement is that it is difficult to dose the airstream such that thetwisted fiber structure is not entrained by the air which flows off inaxial direction of the yarn withdrawal rolls. Should that happen, thenthere can arise the undesired situation that the twisted fiber structureis not engaged by the yarn withdrawal rolls.

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind, it is a primary object of thepresent invention to provide a new and improved construction of a devicefor start spinning, namely, starting or recommencing spinning of a yarnin a friction spinning apparatus which is not afflicted with theaforementioned drawbacks and limitations of the prior art constructions.

Another and more specific object of the present invention relates to anew and improved construction of a device for starting or recommencingspinning of a yarn in a friction spinning apparatus which isuncomplicated in its construction and operation and can be designed towork with relatively simple means.

Yet a further significant object of the present invention is directed toa new and improved construction of a device for starting or recommencingspinning of a yarn in a friction spinning apparatus and containingstructure for the controlled infeed of an airstream in a prescribedmanner such that there is reliably directed, the twisted fiber structuretowards and into engagement with a yarn withdrawal facility, such asyarn withdrawal rolls.

A further significant object of the present starting or recommencingspinning of a yarn in a friction spinning apparatus, wherein suchstarting or recommencing operation can be accomplished with greatreliability and through the use of relatively simple structuralcomponents so that such device is not only simple in design andrelatively inexpensive to fabricate, but requires a minimum ofmaintenance and servicing.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the device for starting or recommencing spinning ismanifested, among other things, by the features that the device forstart spinning comprises a pressure air infeed channel, the air outflowopening of which is directed towards the yarn formation position and theflow direction of which is directed such that the dynamic or backpressure arising from the airflow or airstream is divided into two forcecomponents of different magnitudes, wherein the larger force componentacts in the withdrawal direction of the yarn. Furthermore, there isprovided, a yarn guide element between the friction spinning means andthe yarn withdrawal roller pair by means of which there is guided thetwisted fiber structure and a portion of the air flow or airstream ofthe pressure air infeed channel.

Certain of the more notable advantages afforded by the present inventionreside in the fact that the device for starting or recommencing spinningof the yarn or the like in the friction spinning apparatus is relativelysimple by virtue of the fact that there is afforded the possibility ofperforming the starting of, or recommencing of, the spinning operationat production speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein throughout the various figures of thedrawings, there have been generally used the same reference charactersto denote the same or analogous components and wherein:

FIG. 1 illustrates the general construction of a friction spinningapparatus depicted part schematically and in perspective view andsubstantially corresponding to the friction spinning apparatus describedin cross-referenced U.S. Pat. No. 4,680,924;

FIG. 2 illustrates part of the friction spinning apparatus of FIG. 1 inlongitudinal direction;

FIG. 3 shows part of the friction spinning apparatus depicted in FIG. 1and illustrated in front view, looking in the direction of the arrow Iof FIG. 2;

FIG. 3a illustrates a modification of the friction spinning apparatus ofFIG. 1 but in a showing as depicted in FIG. 3;

FIG. 4 illustrates in section a modification of part of the frictionspinning apparatus of FIG. 1;

FIG. 5 illustrates the friction spinning apparatus depicted in FIG. 1,showing only a portion thereof and illustrated from the opposite side,portraying one of the operating or method stages of the start (startingor recommencing of the) spinning operation;

FIGS. 6 and 7 illustrate the friction spinning apparatus depicted inFIG. 1, in various operating or method stages of the start (starting orrecommencing of the) spinning operation,

FIGS. 8 to 11 respectively illustrate exemplary embodiments of theinventive construction of the friction spinning apparatus depicted inFIG. 1 in a view similar to the showing of FIG. 2;

FIG. 12 illustrates a further exemplary embodiment of the inventiveconstruction of the friction spinning apparatus of the arrangement ofFIG. 1 in a view similar to the showing of FIG. 2 and in combinationwith the detail depicted in FIG. 11; and

FIG. 13 illustrates a modification which is possible for the frictionspinning apparatuses depicted in FIGS. 1 to 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, it is to be understood that to simplify theshowing thereof, only enough of the structure of the device for startingor recommencing of spinning as well as the related friction spinningapparatus has been illustrated therein as is needed to enable oneskilled in the art to readily understand the underlying principles andconcepts of the present invention. It is here further remarked that theterm "start spinning" or equivalent expressions as employed hereinafter,mean either the starting of spinning or piecing after a yarn break inorder to recommence spinning.

Turning attention now specifically to FIG. 1 of the drawings, thegeneral construction of the friction spinning apparatus illustratedtherein by way of example and not limitation, will be seen to comprisesubstantially like the friction spinning apparatus described in theinitially cross-referenced U.S. Pat. No. 4,680,924, a fiber sliveropening device 1 known from the rotor open-end spinning technique orart, which contains a conventional opening roller (not shown) and whichtherefore has been merely generally indicated or represented by itsdrive shaft 1.1. This fiber sliver opening device 1 contains an infeedopening A for receiving a fiber sliver (not shown) or other suitablefiber material. By means of a fiber infeed or transport duct or passage2 adjoining the fiber sliver opening device 1, freely floating fibersare delivered to a rotatable and driveable perforated friction spinningdrum or roll 3 by means of an airstream or airflow which flows throughthe fiber infeed duct or passage 2. As shown in FIG. 2, a yarn end 5.1is formed at a yarn formation position or location 7 on the frictionspinning drum 3 and from which there is ultimately produced, a yarn 5 orthe like.

A counter roll or drum 4 which is also rotatable and driveable isarranged without contacting but in very close disposition with respectto the friction spinning drum or roll 3 and substantially parallelthereto (for example, with a pacing between 0.05 and 0.15 mm). Thecounter roll or drum 4 serves as an aid for twisting-in the fibers atthe yarn formation position or location 7 located in the convergent zoneor nip of the two drums or rolls 3 and 4. The spun yarn 5 is withdrawnby yarn withdrawal means, here shown in the form of a withdrawal rolleror roll pair 6. Such structure is known from earlier publications inthis technology and constitutes state-of-the-art arrangements forfriction spinning equipment, and thus, will not further be describedherein. For example, the commonly assigned European Published PatentApplication No. 0,175,862, published Apr. 2, 1986, shows a basicallysimilar technique and thus reference may be readily had to suchdocument, the disclosure of which is incorporated hereinafter.

Furthermore, in addition to the fiber infeed or transport duct orpassage 2, a pressure air infeed channel or duct 8 opens over the yarnformation position or location 7 in the convergent region of the twofriction spinning drums 3 and 4 (also referred to in the art as frictionspinning rolls 3 and 4). The length G of the exit or outlet opening 9 ofthe pressure air infeed channel 8 corresponds at least to the length F(FIG. 1) of the perforated region P of the perforated friction spinningdrum 3, while the length H of the exit or outlet opening 22 of the fiberinfeed duct or passage 2 corresponds at most to the length F of theperforated region. This perforated region P is illustrated onlypartially in FIG. 1 for simplicity of drawing representation.

The relation of the distance D or D.1 (FIG. 3 or 3a) between the exit oroutlet opening 9 of the pressure air infeed channel 8 and the yarn end5.1 located in the yarn formation position or location 7 to theintensity or energy of the air jet at the exit or outlet opening 9 ofthe pressure air infeed channel 8 must be determined empirically on thebasis of the subsequently described method or operational steps for thestart spinning operation.

The same applies for the not particularly referenced width or breadthand form of the exit or outlet opening 9 of the pressure air infeedchannel 8, the term "form" referring to the configuration or formationof the exit opening surface, to enable variability of the intensity ofthe airstream or air flow at such exit or outlet opening 9. By way ofexample, the width or breadth of the exit or outlet opening 9 can bevaried along the length of such exit or outlet opening 9 in order toobtain differences in the air blowing effect or action along the exit oroutlet opening 9.

As shown in FIG. 2, the pressure air infeed channel 8 also has aconnecting stud or connection 10 by means of which the pressure airinfeed channel 8 is connectable to a suitable and thus herenon-illustrated pressure air network or source comprising conventionalelements or structure for regulating the air pressure and the airquantity and for the control of the airstream or air flow.

FIG. 3a shows a modification of the arrangement of FIGS. 1 to 3a,wherein it is noted that by altering the distance or spacing D.1, theexit or outlet opening 9 of the pressure air infeed channel 8 can bespaced further from the yarn end 5.1 than the exit or outlet opening 22of the fiber infeed duct or passage 2 which is shown spaced by thedistance K from such yarn end 5.1.

Furthermore, in FIG. 3, the modified positioning of the pressure airinfeed channel 8.1 indicated with dash-dotted lines, demonstrates thatthe position of the pressure air infeed channel is not limited to theposition of the pressure air infeed channel 8 illustrated in full lines,and such modification does not involve any substantial reduction in thesubsequently described blowing effect or action.

In the following description, there will be considered the procedure forstart spinning at the time of a fresh spinning operation, in otherwords, the start of the thread break, in other words, recommencement ofthe spinning operation.

First, it should be mentioned that the airstream or air flow previouslydescribed and which prevails in the fiber infeed duct or passage 2 forforwarding the fibers 11 from the (non-illustrated) opening roll formingpart of the opening device 1 to the friction spinning drum 3 isgenerated in known manner by a suction nozzle 23 (FIGS. 3 and 3a) orequivalent suction facility located in the friction spinning drum 3.This suction nozzle 23 generates at the surface 3a of the frictionspinning drum 3 over the length F of the perforated region P, a suctionairstream or air flow within which there is located, the yarn end 5.1and the exit or outlet opening 22 of the fiber infeed duct or passage 2.

As particularly well shown in FIG. 5, during start spinning, the fibers11 are first fed by means of the fiber infeed duct or passage 2 onto thesurface 3a of the friction spinning drum 3 without at first withdrawingthese fibers as a yarn. Accordingly, there is built-up, a rotatingtwisted fiber structure or rotating fiber lap 12 of steadily increasingsize.

In FIG. 5, the counter roll or drum 4 has not been illustrated in orderto facilitate the representation of the twisted fiber structure 12.

Now, when this twisted fiber structure 12 reaches a predeterminate size,a suction device 13 serving as a yarn take-up means or facility ispositioned at the diverging or outlet side 6a of the yarn withdrawalroller pair 6 which rotate in the direction of the arrows illustrated inFIG. 5 in such a manner that the yarn take-up means or suction device 13is able to take-up the twisted fiber structure 12 delivered by the yarnwithdrawal roller pair 6.

In addition, after the twisted fiber structure 12 has reached thepreviously mentioned preset size, pressure air is delivered through thepressure air infeed channel 8, so that the twisted fiber structure 12 isreliably and positively passed into the infeed opening 14 (see, forinstance, FIG. 2) of a guide tube or tube member 15 and through thisguide tube 15 into the converging space of the rotating yarn withdrawalroller pair 6.

As seen in FIGS. 1 and 2, the guide tube or tube member 15 is providedbetween the end faces 3b of the friction drums or rolls 3 and 4 and theyarn withdrawal rollers or roller pair 6 in such a manner that the notparticularly referenced axis of symmetry of the guide tube or tubemember 15 lies substantially in an imaginary plane which contains theline of contact of the two yarn withdrawal rollers or roller pair 6 andthe position or location on the friction spinning therefrom formed spunyarn 5 leave this friction spinning drum 3.

The inner or internal diameter of the guide tube 15 is larger than theexternal diameter of the previously mentioned twisted fiber structure12, for example, it may be twice as large.

The exit opening 15a of the guide tube or tube member 15 can be, asshown in FIG. 2, provided with cut-away portions 15b such that this exitopening 15a is adapted to the peripheral surface or curvature of theyarn withdrawal rollers or roller pair 6.

Furthermore, as illustrated in FIG. 4, the guide tube or tube member,there designated by reference numeral 15.1, can be designed to form aninjector guide passage or guide tube. In this case, pressure airopenings or ports 16 and 17 are provided at the wall of the guide tubeor tube member 15.1 which impart to an airstream or air flow guided orflowing through these pressure air openings or ports 16 and 17, a forcecomponent acting in the yarn withdrawal direction Z.

The aforesaid airstream or air flow is generated by an annular orring-shaped pressure chamber 18 provided around these pressure airopenings or ports 16 and 17 defining blowing openings and which issubjected to above-atmospheric pressure. The annular or ring-shapedpressure chamber 18 is fed by a connecting bore or channel 19 from anon-illustrated pressure air system or source. A connecting orconnection tube 20 is fixedly connected with a pressure housing orhousing member 21 containing the pressure chamber 18 and the connectingbore or channel 19.

The pressure housing 21, in turn, serves for fixedly receiving theinjector guide tube or passage 15.1 and it seals the pressure chamber 18against the atmosphere.

The injector guide tube or passage 15.1 (FIG. 4) therefore has, inrelation to the guide tube or passage 15 (see FIG. 2), the advantage oftransporting the previously mentioned twisted fiber structure 12positively into the converging zone of the yarn withdrawal rollers orroller pair 6 during the start spinning operation.

After leaving the yarn withdrawal rollers or roller pair 6, the twistedfiber structure 12 is caught and drawn-in by suction by the suctiondevice 13, as illustrated in FIGS. 6 and 7.

The yarn 5 (see FIG. 7), which is subsequently also drawn-in by suction,is guided by means of this suction device 13 to the further elementsforming part of the spinning machine (not shown), and since thesefurther elements are conventional, they need not be here furtherdescribed.

As soon as the twisted fiber structure 12 has been caught or entrainedby the suction device 13, the airstream or air flow in the pressure airinfeed channel 8 and the airstream or air flow in the injector guidetube or tube member 15.1, are interrupted.

The previously mentioned start spinning operation can be carried out atfull production speed so that the yarn delivered by the yarn withdrawalrollers or roller pair 6 corresponds to the yarn which is to be producedin practice.

It will be clear that the described operation also can be carried outwith friction spinning apparatuses having a friction spinning disk inplace of the friction spinning drums and using as the counter element, aconical or frusto-conical roll or drum. In that case, the fibers aretransported to the friction spinning disk and the yarn is formed on thefriction spinning disk, cooperating with the conical or frusto-conicalroll or drum, at a yarn formation position and is withdrawn therefrom byyarn withdrawal rollers. Such a device is illustrated and described, forinstance, in British Patent Specification No. 1,231,198, published May12, 1971.

Also, in place of a friction spinning drum or disk, it is possible touse an appropriately perforated band or belt (not shown) on which thefibers are delivered to a yarn formation position or location lying atsubstantially right angles to the direction of movement of theperforated band or belt, in order to thus produce a yarn.

Such a friction spinning apparatus equipped with the aforedescribedperforated band or belt, has been described and illustrated in FrenchPatent No. 2,480,799, published Oct. 23, 1981.

Furthermore, in place of the suction device or unit 13, there can beused, a suitable mechanical take-up device (not shown). This mechanicaltake-up device merely must be capable of taking-up the twisted fiberstructure 12 and the yarn 5 joined thereto at production speed and inthe previously described manner.

Furthermore, it has bee found in practice, that an airstream or air flowof predeterminate intensity delivered by the pressure air infeed channel8, the intensity being sufficient to grasp a twisted fiber structure 12of predeterminate size and to forward it towards the yarn withdrawalrollers or roller pair 6, only becomes practically effective when thetwisted fiber structure 12 has reached an adequate size and such sizemust be empirically determined.

From the foregoing explanations, it is possible to conclude that theairstream or air flow from the pressure air infeed channel 8 can bestarted simultaneously with or before the transport of the fibers 11 tothe friction spinning drum 3.

Furthermore, it has been determined that the airstream or air flow hasno negative influence or effect on the yarn produced or generated afterthe start spinning operation.

Accordingly, it is possible to appropriately select as desired, thesequence of operations as regards start-up of fiber transport andstart-up of the airstream or air flow, or maintenance or switching-offof the airstream or air flow after the start spinning operation.

Advantageously, the sequence of operations is selected such that firstthe fibers 11 are delivered and the airstream or air flow is switched-ononly after a twisted fiber structure 12 of desired or predeterminatesize has been obtained.

Furthermore, switching-on of the airstream or air flow before deliveryof fibers 11 can be used if required or desired, to clean the surface ofthe friction spinning drum 3 and the counter roller or drum 4. Inaccordance with the previous discussion, this cleaning airstream or airflow can be selectively maintained before delivery of the fibers 11 orswitched-off before such fiber delivery.

In FIG. 2, the dot-dash line S indicates the central flowline of theairstream or air flow guided in the pressure air infeed channel or duct8 and the angle α indicates that this flowline S lies at an inclinationto the there shown yarn end 5.1 such that the dynamic or back-pressurearising from the aforesaid airstream or air flow thus generates a forcecomponent R directed towards the yarn withdrawal rollers or roller pair6 and acting on the twisted fiber structure 12. The angle α isadvantageously selected smaller than 45°.

In any event, it will be appreciated that the pressure air infeedchannel or duct 8 possesses a flow direction for the airstream whichflows therethrough which is directed such that the dynamic pressurearising from the flow of the airstream is dividable into two forcecomponents of different magnitudes defining a larger force component anda smaller force component. The larger force component, designated byreference character R, acts in the yarn withdrawal direction indicatedby the arrow Z in FIG. 2.

FIGS. 8 and 9 show exemplary embodiments of the inventive constructionof the friction spinning apparatus in which the guide tube or tubemember 15a or 15.1a (FIG. 8) or 15b or 15.1b (FIG. 9), as viewed in theyarn withdrawal direction Z, has venting openings 26 (FIG. 8) and 27(FIG. 9), respectively, in those tube halves or regions directed towardsthe yarn withdrawal roller pair 6. These venting openings 26 or 27, asthe case may be, enable substantial avoidance of the possibility thatthe main quantity of the air flowing in the guide tube or tube member15a or 15.1a (FIG. 8) or 15b or 15.1b (FIG. 9) flows in the axialdirection of the yarn withdrawal rollers or roller pair 6 in theconvergent space of such yarn withdrawal roller pair 6. As a function ofthe necessary air quantity and the weight of the twisted fiber structure12, such would have the disadvantage that the twisted fiber structure 12would also be undesirably diverted by means of the air and would not becaught or seized by the yarn withdrawal roller pair 6.

This escape of the air through the respective venting openings 26 and 27can be additionally augmented by a suction device 24 (indicated withdot-dash lines in FIGS. 8 and 9) provided at the region of these ventingopenings 26 and 27. This suction device 24 surrounds the related guidetube 15a or 15.1a (FIG. 8) or 15b or 15.1b (FIG. 9) such that the air issucked away essentially evenly at the periphery of the related guidetube through the venting openings 26 and 27, as the case may be.

On the other hand, a graded or stepped suction effect can beadvantageous in which case, for example, the perforation intensity ordistribution increases in the yarn withdrawal direction Z. By virtue ofthis design, the air delivery can be increased without affording thetwisted fiber structure 12 the opportunity to escape in the axialdirection of the yarn withdrawal rollers or roller pair 6. The speed ofthe transporting air must, however, be selected such that the twistedfiber structure 12 does not remain caught on the internal wall of theassociated guide tube or tube member.

In FIG. 8, the venting openings are provided in the form of bores orround apertures 26 or the like and in FIG. 9 in the form of slots orslits 27 or the like.

As previously mentioned, the guide tubes 15 and 15.1 depicted in FIGS.1, 2, 4, 5, 6 and 7 can be provided with the venting openings 26 or 27,as the case may be. Consequently, it will be observed that there can beprovided, the combination of the suction device 24 with the pressure airopenings or ports 16 and 17 and the pressure housing 21 associatedtherewith. In order to distinguish these various possibilities ofconstructions, the guide tubes, it will be observed, and as notedpreviously, in FIG. 8, the guide tube or tube member is indicated byreference characters 15a and 15.1a, and in FIG. 9, by referencecharacters 15b and 15.1b.

The stepwise increase in the venting of the guide tube or tube member15b or 15.1b (FIG. 9) can be, as indicated with the dotted or phantomlines, generated by lengthening the individual slots 27.

A further modification of the type of venting structure shown in FIGS. 8and 9 is indicated in FIG. 10 in which in the region of the yarnwithdrawal rollers or roller pair 6, the guide tubes 15 or 15.1,previously considered, are shortened and project into a venting tube ortube member 33 at a predeterminate spacing E from the yarn withdrawalroller pair 6. The shortened guide tubes or tube members have beenindicated in FIG. 10 by reference characters 15c and 15.1c,respectively. The internal diameter B of the venting diameter C of theguide tube or tube member 15c or 15.1c, as the case may be, such thatthe air speed or velocity of the air in the venting tube or tube member33 is exactly sufficient to forward the twisted fiber structure 12 ontothe rotating peripheral surface of the yarn withdrawal rollers or rollerpair 6 so that the twisted fiber structure 12 can pass into the clampingnip of the yarn withdrawal rollers or roller pair 6. Due to thedifference between the internal diameter B and the external diameter Cthere is formed an annular or ring-shaped venting opening or gap 35. Thespacing E is advantageously at least as large as the aforementioneddifference between the dimensions B and C.

As indicated with dot-dash lines in FIG. 10, it is also possible to usethe suction device 24, but here indicated by reference character 24.1 inFIG. 10, to draw away air flowing out between the guide tube or tubemember 15c or 15.1c and the venting tube or tube member 33. This suctiondevice 24.1 here surrounds the venting tube or tube member 33 and alsothe related guide tube or tube member 15c or 15.1c and, in view of thisdifference with respect to the suction device 24 of FIGS. 8 and 9, suchsuction device as above-noted, has been indicated with the referencenumeral 24.1.

A further embodiment, which provides a modified function of the guidetube or tube member 15 is illustrated in FIG. 11 by the guide trough ortrough member 25. As shown in FIG. 11, this guide trough or troughmember 25 is closed-off downwardly and is open upwardly, and can have,for instance, either a substantially V-shape or substantially U-shape insection. Advantageously, the base 28 of the guide trough or troughmember 25 is only slightly deeper than the stretched-out extended yarnguide line of the twisted fiber structure 12, as illustrated in FIG. 11.

A further advantageous embodiment illustrated in FIG. 12 in combinationwith the guide trough or trough member 25 consists of an elongation ofthe pressure air infeed channel 8 in the direction of the yarnwithdrawal rollers or roller pair 6 in the manner illustrated withdotted lines and indicated by reference numeral 8.1, so that thepressure air is not only directed towards the yarn formation positionbut also into the guide trough or trough member 25. On the other hand,as illustrated by the spacing M, the pressure air infeed channel 8.1should only be extended to a given distance towards the yarn withdrawalrollers or roller pair 6 in order to afford the infed or blown-in air,the opportunity to escape in such a manner that the main air quantitycan escape upwardly out of the guide trough or trough member 25 asviewed in FIG. 12.

FIG. 13 shows a possible modification for the arrangements of FIGS. 1 to7 in that the upper yarn withdrawal roller or roll 6b, as viewed in thevarious FIGS. 1, 2, 4, 5, 6, 7, 8, 9 10, 11 and 12, is made raisable orelevatable. This upper roll raising action can be performed by anysuitable type of conventional displacement or elevating means, forexample, a fluid operated, such as a pneumatic cylinder or cylinder unit29. The displacement or elevating means, here the pneumatic cylinder orcylinder unit 29, is connected by pivot or joint means, on the one hand,with a stationary housing portion 30 and, on the other hand, with apivot lever 31 connected to the upper yarn withdrawal roll 6b. Thispivot lever or lever member 31 is also pivotably mounted at its end 32in a suitable stationary housing portion (not shown). Swinging-up orupward pivoting of the upper yarn withdrawal roller or roll 6b of theyarn withdrawal roller pair 6 is carried out only for a short time sothat the twisted fiber structure 12 can be passed through. By means ofthis roll raising or lifting action, there is obtained the possibilitythat the air flowing through the guide tube or tube member, such as theguide tube 15 or 15.1, does not have to flow in the axial direction ofthe yarn withdrawal rollers or roller pair 6.

It will be clear that the lifting of the upper yarn withdrawal roller orroll 6b of the yarn withdrawal roller pair 6 illustrated in FIG. 13 alsocan be combined with the devices or structures of FIGS. 8 to 12.

A modification of the guide tubes or tube members 15, 15.1, 15a, 15.1a,15b, 15.1b, 15c and 15.1c resides in forming the corresponding guidetube either along its complete length or in the front halves or regions,as viewed in the direction of forward travel of the yarn or yarnwithdrawal direction Z, with a conical form or configuration, as simplyrepresentively indicated in FIG. 5 by reference character 15d, for thusreducing the tube section or cross-sectional area.

As can be seen from the various modifications, the inventive teachingsand concepts are not limited to the illustrated examples andmodifications thereof are readily possible.

Thus, while there are shown and described present preferred embodimentsof the invention, it is to be distinctly understood that the inventionis not limited thereto, but may be otherwise variously embodied andpracticed within the scope of the following claims.

What we claim is:
 1. A device for performing a start spinning operationentailing starting or recommencing spinning of a yarn in a frictionspinning apparatus, wherein:said friction spinning apparatuscomprises:friction spinning means provided with a friction spinningsurface; said friction spinning means defining a yarn formation positionat which there is formed a twisted fiber structure; means for deliveringfibers to the friction spinning surface of the friction spinning means;the fibers being formed into the twisted fiber structure at the yarnformation position during the start spinning operation; yarn withdrawalmeans for withdrawing the twisted fiber structure in the form of a yarnin a yarn withdrawal direction; said device for performing the startspinning operation comprising: a pressure air infeed channel having anoutflow opening directed towards the yarn formation position and throughwhich flows an airstream; said pressure air infeed channel possessing aflow direction for the airstream flowing therethrough which is directedsuch that dynamic pressure arising from the flow of the airstream isdivisible into two force components of different magnitudes defining alarger force component and a smaller force component; the larger forcecomponent acting in the yarn withdrawal direction of the yarn; a yarnguide element provided between the friction spinning means and the yarnwithdrawal means for guiding the twisted fiber structure and a portionof the airstream of the pressure air infeed channel; said yarn guideelement containing a portion directed towards said yarn withdrawalmeans; air venting means provided in said yarn guide element in saidportion directed towards said yarn withdrawal means; and said airventing means preventing the main quantity of the portion of theairstream flowing through said yarn guide element, from diverting thetwisted fiber structure from said yarn withdrawal means.
 2. The deviceas defined in claim 1, wherein:said yarn withdrawal means comprises ayarn withdrawal roller pair.
 3. The device as defined in claim 2,wherein:said yarn guide element comprises a yarn guide tube.
 4. Thedevice as defined in claim 3, wherein:said yarn guide tube includes ayarn guide tube portion directed towards said yarn withdrawal rollerpair; and said air venting means constituting venting openings at saidyarn guide tube portion which is directed towards said yarn withdrawalroller pair.
 5. The device as defined in claim 4, wherein:said ventingopenings are defined by bores; and said yarn guide tube opens in spacedrelationship from and onto said yarn withdrawal roller pair and in closeproximity thereto.
 6. The device as defined in claim 5, wherein:saidyarn guide tube is structured in conformity to the curvature of the yarnwithdrawal roller pair such that said yarn guide tube can be positionedin the immediate region of said yarn withdrawal roller pair.
 7. Thedevice as defined in claim 5, wherein:said yarn guide tube is providedwith air inflow means located in a portion thereof directed towards saidfriction spinning means and having an airflow directional component inthe yarn withdrawal direction.
 8. The device as defined in claim 4,wherein:said venting openings are defined by venting slots; said yarnguide tube opens in spaced relationship from and onto said yarnwithdrawal roller pair and in close proximity thereto.
 9. The device asdefined in claim 8, wherein:said yarn guide tube is structured inconformity to the curvature of the yarn withdrawal roller pair such thatsaid yarn guide tube can be positioned in the immediate region of saidyarn withdrawal roller pair.
 10. The device as defined in claim 8,wherein:said yarn guide tube is provided with air inflow means locatedin a portion thereof directed towards said friction spinning means hadhaving an airflow directional component in the yarn withdrawaldirection.
 11. The device as defined in claim 3, wherein:said yarn guidetube has an end portion situated adjacent said yarn withdrawal rollerpair; a venting tube constituting said air venting means and positionedto cooperate with said end portion of said yarn guide tube; said ventingtube surrounding the end portion of said yarn guide tube situatedadjacent said yarn withdrawal roller pair; said venting tube having aninternal diameter; said yarn guide tube having an external diameter; theinternal diameter of said venting tube being larger by a given valuethan the external diameter of the yarn guide tube to thus form anannular venting opening for said yarn guide tube; said venting tubeopening in spaced relationship from and onto said yarn withdrawal rollerpair as in close proximity thereto; and said yarn guide tube projectingwith a predetermined spacing toward said yarn withdrawal roller pairinto said venting tube.
 12. The device as defined in claim 11,wherein:said yarn guide tube is structured in conformity to thecurvature of the yarn withdrawal roller pair such that said yarn guidetube can be positioned in the immediate region of said yarn withdrawalroller pair.
 13. The device as defined in claim 11, wherein:said yarnguide tube is provided with air inflow means located in a portionthereof directed towards said friction spinning means and having anairflow directional component in the yarn withdrawal direction.
 14. Thedevice as defined in claim 3, wherein:said yarn guide tube possesses asubstantially conical configuration at least at a predeterminate regionthereof in order to reduce the cross-sectional area of the yarn guidetube in the yarn withdrawal direction.
 15. The device as defined inclaim 2, wherein:said yarn guide element comprises a guide troughdefining an open side which constitutes said air venting means.
 16. Thedevice as defined in claim 15, wherein:said pressure air inflow channelextends into the region of said yarn guide trough.
 17. The device asdefined in claim 2, further including:means for opening said yarnwithdrawal roller pair for the start spinning operation.
 18. A devicefor performing a start spinning operation entailing starting orrecommencing spinning of a yarn in a friction spinning apparatus,wherein:said friction spinning apparatus comprises: friction spinningdrums provided with a friction spinning surface; said friction spinningdrums defining substantially between and along the friction spinningdrums a yarn formation position at which there is formed a twisted fiberstructure; means for delivering fibers to the friction spinning surfaceof the friction spinning means; the fibers being formed into the twistedfiber structure at the yarn formation position during the start spinningoperation; a yarn withdrawal roller pair for withdrawing the twistedfiber structure in the form of a yarn in a yarn withdrawal direction;said device for performing the start spinning operation comprising: apressure air infeed channel having an outflow opening directed towardsthe yarn formation position and through which flows an airstream; saidpressure air infeed channel possessing a flow direction for theairstream flowing therethrough which is directed such that dynamicpressure arising from the flow of the airstream is divisible into twoforce components of different magnitudes defining a larger forcecomponent and a smaller force component; the larger force componentacting in the yarn withdrawal direction of the yarn; a yarn guide tubeprovided between the friction spinning drums and the yarn withdrawalroller pair for guiding the twisted fiber structure and a portion of theairstream of the pressure air infeed channel; said yarn guide tubeincludes a yarn guide tube portion directed towards said yarn withdrawalroller pair; and said yarn guide tube being provided with ventingopenings at said yarn guide tube portion which is directed towards saidyarn withdrawal roller pair.